i) Field of the Invention
The present invention relates to a magnetic recording medium in which information is magnetically recorded, a method of manufacturing the magnetic recording medium, and an information regeneration apparatus for regenerating the information recorded in the magnetic recording medium.
ii) Description of Related Art
In recent years, with spread of computers, a large amount of information has been handled in a daily manner, and as one of apparatuses for recording/regenerating a large amount of information, a hard disk drive (HDD) has been used.
The HDD incorporates a magnetic disk as a disk-like magnetic recording medium in which the information is recorded, and a magnetic head for recording/regenerating the information in the magnetic disk.
FIG. 1 is a diagram showing a positional relation between the magnetic recording medium and the magnetic head in the HDD.
FIG. 1 shows a magnetic disk 20, and a head slider 30 floated from the magnetic disk 20 and provided with a magnetic head 31 in the vicinity of an end thereof.
In the magnetic disk 20, an underlayer 12 constituted of Cr, and the like is formed on a nonmagnetic substrate 11, and a magnetic layer 13 of a material indicating ferromagnetism is formed on the underlayer 12. The magnetic layer 13 is divided into a plurality of micro areas, and carries information in accordance with magnetization directions in the respective micro areas. Moreover, the magnetic layer 13 is covered and protected by a protective layer 14 formed of carbon and the like and a lubricating layer 15 of perfluoropolyether (PFPE) and the like. During operation of HDD, the magnetic disk 20 is in a rotating state.
For the head slider 30, a floating surface facing the magnetic disk 20 is covered and protected by a protective film 32, for example, of carbon. The head slider 30 and the magnetic head 31 included in the head slider 30 are disposed in the vicinity of the magnetic disk 20, and during starting/stopping of rotation of the magnetic disk, the floating surface contacts the surface of the magnetic disk 20 to slide thereon, but during operation, as shown in FIG. 1, a floating state above the rotating magnetic disk 20 is obtained.
The magnetic head 31 generates a magnetic field in accordance with a signal current from the outside, appropriately reverses each magnetization of each micro area of the magnetic disk to record information, and reads the respective magnetization directions of the magnetic disk 20 to regenerate the information.
A recording density of the information recorded in the magnetic disk is enhanced every year, and a magnetic disk in which recording with a higher recording density is possible has been demanded. As one factor necessary for enhancing the recording density, as shown by an arrow in FIG. 1, a distance (magnetic spacing) between the magnetic layer 13 of the magnetic disk and the magnetic head 31 is reduced. In recent years, the magnetic spacing of about 50 nm has been realized, but in order to enhance the recording density, the magnetic spacing needs to further be reduced.
The reduction of the magnetic spacing is realized, for example, by thinning the protective layer 14. In recent years, in order to reduce the magnetic spacing, the protective layer of the magnetic disk is formed with a very thin film having thickness of about a dozen or so nanometers over the entire surface of the disk, but to further reduce the magnetic spacing, it has been requested to set the thickness of the protective layer to 10 nm or less.
However, when the protective layer with a thickness of 10 nm or less is formed, for example, using an amorphous carbon based material by a sputtering process, the formed protective layer is insufficient in film hardness and surface coverage, cannot maintain stable friction/abrasion properties for a long period and is disadvantageously inferior in contact sliding durability. Moreover, in a case in which the protective layer with a thickness of 10 nm or less is formed using the amorphous carbon based material by a plasma CVD process which is known to form the film with higher hardness and higher coverage rate than those of the sputtering process, in a thin film area of several nanometers, in spite of the high hardness of the protective layer itself, the hardness of the underlying magnetic layer influences a surface hardness, as a result the hardness of the medium surface is reduced, and there still occurs a problem that the contact sliding durability is deteriorated.
The present invention has been developed in consideration of the aforementioned circumstances, and an object thereof is to provide a magnetic recording medium in which reduction of a magnetic spacing and securing of a contact sliding durability are compatible with each other, a magnetic recording medium manufacture method, and an information regeneration apparatus.
To achieve the aforementioned object according to the present invention there is provided a first magnetic recording medium comprising:
a disk-like substrate;
a magnetic layer consisting of a material indicating ferromagnetism, said magnetic layer being formed on said substrate; and
a protective layer for protecting the magnetic layer, said protective layer being formed in at least one area of an outer peripheral area and an inner peripheral area of a disk excluding a middle area held between the outer peripheral area and the inner peripheral area on said magnetic layer.
The first magnetic recording medium of the present invention is employed, for example, in HDD, the protective layer is disposed only in areas such as the outer peripheral area or inner peripheral area which is brought into contact with a magnetic head in the HDD in a CSS or Load/Unload state, and the protective layer can be provided with a film thickness equal to a conventional film thickness as occasion demands. Therefore, in the first magnetic recording medium of the present invention, contact sliding durability is secured against the magnetic head. Moreover, for the first magnetic recording medium of the present invention, since no protective layer is formed in the middle area or another area with information recorded therein, the magnetic spacing can be reduced by the area with no protective layer formed therein. As described above, in the first magnetic recording medium of the present invention, the reduced magnetic spacing and the contact sliding durability are compatible with each other.
To achieve the aforementioned object according to the present invention there is provided a second magnetic recording medium comprising:
a disk-like substrate;
a magnetic layer consisting of a material indicating ferromagnetism, wherein a surface layer portion is modified by introducing a predetermined element, said magnetic layer being formed on said substrate; and
a protective layer for protecting the magnetic layer, said protective layer being formed in at least one area of an outer peripheral area and an inner peripheral area of a disk excluding a middle area held between the outer peripheral area and the inner peripheral area on the modified surface layer portion of said magnetic layer.
Similarly as the first magnetic recording medium of the present invention, the second magnetic recording medium of the present invention is employed, for example, in the HDD, the protective layer is disposed only in the areas such as the outer peripheral area or inner peripheral area which is brought into contact with the magnetic head in the HDD in the CSS or Load/Unload state, and the protective layer can be provided with the film thickness equal to the conventional film thickness as occasion demands. Therefore, in the second magnetic recording medium of the present invention, the contact sliding durability is secured against the magnetic head. Moreover, for the second magnetic recording medium of the present invention, no protective layer is formed in the middle area or another area with information recorded therein, and the magnetic layer is protected by setting the surface layer portion of the magnetic layer to be thinner than the protective layer and uniformly modifying the surface layer portion. Therefore, in the second magnetic recording medium of the present invention, the magnetic spacing can be reduced by the area with no protective layer formed therein. Moreover, since the surface layer portion of the magnetic layer is modified, protection of the magnetic layer can more firmly be performed. As described above, in the magnetic recording medium of the present invention, the reduced magnetic spacing and the contact sliding durability are compatible with each other.
For the second magnetic recording medium of the present invention, in the magnetic layer, the surface layer portion is preferably modified by introducing at least one element selected from an element group consisting of nitrogen, oxygen, and fluorine.
Since nitrogen and oxygen are introduced to the surface layer portion of the magnetic layer, for the surface layer portion, hardness is raised, and insulation properties are enhanced. Moreover, since fluorine is introduced to the surface layer portion of the magnetic layer, for the surface layer portion, the hardness is raised, and friction coefficient is reduced. Moreover, to secure the insulation properties of the magnetic recording medium surface and further reduce the friction coefficient, the lubricating layer including fluorine is sometimes formed on the magnetic layer, and by introducing fluorine to the surface layer portion of the magnetic layer, the lubricating film is satisfactorily held on the magnetic layer.
For the first and second magnetic recording mediums of the present invention, the protective layer is preferably consisting of an amorphous carbon based material.
The protective layer of the material is high in hardness and superior in durability against sliding with the magnetic head or the like.
Moreover, the first and second magnetic recording mediums of the present invention are preferably provided with a lubricating layer formed on the magnetic layer and protective layer, said lubricating layer consisting of a fluorine based lubricant.
By the presence of the lubricating layer, the friction coefficient between the head and the magnetic recording medium is reduced, and sliding durability of the magnetic recording medium is enhanced. Moreover, the insulation properties of the magnetic recording medium are also secured.
Furthermore, in the first and second magnetic recording mediums of the present invention, the protective layer is preferably consisting of a carbon film to which at least one element selected from an element group consisting of hydrogen, nitrogen, and fluorine is introduced.
By introducing hydrogen, nitrogen and fluorine to the protective layer, abrasion resistance of the protective layer is enhanced. Moreover, when fluorine is introduced to the protective layer, and the lubricating layer is formed on the protective layer, adhesion properties of the lubricating layer and protective layer are enhanced.
For the first and second magnetic recording mediums of the present invention, the protective layer is preferably consisting of a carbon film to which hydrogen is introduced in such a manner that a Cxe2x80x94H bond content is 15xc3x971021/cm3 or less.
With the Cxe2x80x94H bond content, the protective layer is provided with a sufficient sliding durability as described later in an embodiment.
To achieve the aforementioned object according to the present invention there is provided a first magnetic recording medium manufacture method comprising:
a magnetic layer forming step of forming a magnetic layer including a ferromagnetic material on a disk-like substrate; and
a protective layer forming step of forming a protective layer for protecting the magnetic layer in at least one area of an outer peripheral area and an inner peripheral area of a disk excluding a middle area held between the outer peripheral area and the inner peripheral area on the magnetic layer formed in the magnetic layer forming step.
According to the first magnetic recording medium manufacture method of the present invention, similarly as the first magnetic recording medium of the present invention, a magnetic recording medium is manufactured in which the reduced magnetic spacing and the contact sliding durability are compatible with each other.
To achieve the aforementioned object according to the present invention there is provided a second magnetic recording medium manufacture method comprising:
a magnetic layer forming step of forming a magnetic layer consisting of a material indicating ferromagnetism on a disk-like substrate;
a modifying step of introducing a predetermined element onto the magnetic layer formed by said magnetic layer forming step to modify a surface layer portion of the magnetic layer; and
a protective layer forming step of forming a protective layer for protecting the magnetic layer in at least one area of an outer peripheral area and an inner peripheral area of a disk excluding a middle area held between the outer peripheral area and the inner peripheral area on the surface layer portion of the magnetic layer modified by said modifying step.
According to the second magnetic recording medium manufacture method of the present invention, similarly as the second magnetic recording medium of the present invention, the magnetic recording medium is manufactured in which the reduced magnetic spacing and the contact sliding durability are compatible with each other.
In the second magnetic recording medium manufacture method of the present invention, the modifying step preferably comprises subjecting the surface layer portion of the magnetic layer formed by the magnetic layer forming step to at least one treatment of a nitrogen plasma treatment, an oxygen plasma treatment, and a CF4 plasma treatment to modify the surface layer portion.
By the nitrogen plasma treatment or the oxygen plasma treatment, for the surface layer portion of the magnetic layer, the hardness is raised, and the insulation properties are enhanced. Moreover, by the CF4 plasma treatment, for the surface layer portion of the magnetic layer, the hardness is raised, and the friction coefficient is reduced. Furthermore, when the lubricating layer of the fluorine-based lubricant is formed on the magnetic layer, the lubricating film is satisfactorily held.
Moreover, in the first and second magnetic recording medium manufacture methods of the present invention, the protective layer forming step preferably comprises forming a hydrocarbon based gas or a mixture gas of a hydrocarbon based gas and a predetermined additive gas into a plasma by a plasma CVD process to form the protective layer.
By the protective layer forming step, even with a film thickness of 10 nm or less, the protective layer is consisting of a dense and hard film.
For magnetic recording apparatuses of the present invention for achieving the aforementioned object, either one of first and second information recording apparatuses is an information recording apparatus for applying a magnetic field to a magnetic recording medium which carries magnetization and reversing a magnetization direction to record information on the magnetic recording medium.
In the first information recording apparatus, the magnetic recording medium comprises the first magnetic recording medium of the present invention.
In the second information recording apparatus, the magnetic recording medium comprises the second magnetic recording medium of the present invention.
In these first and second information recording apparatuses of the present invention, as the respective magnetic recording mediums disposed on the information recording apparatuses, the first, second magnetic recording mediums in which the reduced magnetic spacing and the contact sliding durability are compatible with each other are employed, and either one of the apparatuses is therefore suitable for recording the information with a high recording density.
For information regeneration apparatuses of the present invention for achieving the aforementioned object, either one of first and second information regeneration apparatuses is an information regeneration apparatus having a magnetic recording medium in which information is recorded in accordance with a magnetization direction, and a magnetic head, disposed in the vicinity of the magnetic recording medium, for detecting magnetization directions of respective points of the magnetic recording medium said information regeneration apparatus regenerating the information in accordance with the magnetization directions of the respective points of the magnetic recording medium detected by the magnetic head.
For the first information regeneration apparatus, the magnetic recording medium comprises the first magnetic recording medium of the present invention.
For the second information regeneration apparatus, the magnetic recording medium comprises the second magnetic recording medium of the present invention.
In these first and second information regeneration apparatuses of the present invention, as the respective magnetic recording mediums disposed on the information regeneration apparatuses, the first, second magnetic recording mediums in which the reduced magnetic spacing and the contact sliding durability are compatible with each other are employed, and either one of the apparatuses is therefore suitable for regenerating the information recorded with the high recording density.